The invention relates to a cooling circuit for an internal combustion engine of a motor vehicle including a coolant pump arranged upstream of the engine, a cooler whose inlet is connected to the engine and whose outlet is connected to the pump and a cooler bypass line extending from the engine coolant outlet directly to the coolant pump by-passing the cooler.
Cooling circuits for internal combustion engines are already known in a variety of embodiments. In addition to ensuring the actual operation of a cooling circuit for cooling the internal combustion engine and further components of the motor vehicle and, if appropriate, the utilization of the heated coolant as a heat source for heating devices of an air-conditioning system of the motor vehicle, it is also important for the cooling circuit that it can be vented at various points or components when necessary.
An equalizing tank, for example, is generally provided which is connected inter alia to a venting duct of the cooler and on the one hand ensures a certain coolant quantity in the cooling circuit and on the other hand also provides a venting function. An arrangement of this type is described for example in DE 39 28 477 C2, wherein a turbo-charger is additionally arranged downstream of the internal combustion engine.
In addition, it is disclosed for example in DE 43 42 292 A1 to provide a collecting tank, which is arranged downstream of the internal combustion engine, with a filling line and also a venting line.
DE 39 40 825 C2 discloses a hydrodynamic flow retarder which includes integrated therein in a compact manner a heat exchanger and a collecting tank for the working fluid. The collecting tank is provided with a venting line which is merged with a venting line of the retarder.
In addition, U.S. Pat. Nos. 4,273,081, 4,300,718 and 4,643,134 disclose each a cooling circuit in which a thermostat valve is arranged between the internal combustion engine and the cooler which opens when the coolant temperature in the internal combustion engine exceeds a predetermined temperature. Provided parallel to the thermostat valve is in each case one venting line. In the case of U.S. Pat. No. 4,273,081, the ventilating line is provided with a valve arrangement which closes during the course of the filling process of the internal combustion engine in order to prevent an undesired discharge of the coolant out of the internal combustion engine to the cooler.
In the case of a coolant circuit as specified in the introduction for an internal combustion engine, it is additionally desirable to also be able to vent the coolant line between the cooler and the inlet or suction side of the pump device. In conventional cooling circuits, this is possible only in a complex manner by means of external venting lines and valves.
It is the object of the present invention to provide a simple and cost-effective possibility of ensuring reliable venting of the cooling line between the cooler and the inlet side of the pump device during the filling process of a cooling circuit for an internal combustion engine of the type specified in the introduction.